Optimal clock speed of qubit gate operations on open quantum systems

We report that an optimal speed of gate operations yields maximum fidelity for qubits in open quantum systems. We show that the fast qubit gate operations and achieving high fidelity are not two independent processes in the presence of drive-induced dissipation (DID). The speed of qubit gates cannot in principle be arbitrarily fast without compromising the fidelity of the gate operations. The fidelity is found to be a function of the DID and the relaxation terms arising from the qubit-environment coupling; as a result, it behaves nonmonotonically with the drive amplitude. We show that the competition between these two sources of decoherence, naturally leads to an optimum value of the drive amplitude. The fidelity of the qubit gate becomes maximum at this optimum value of the drive amplitude. To incorporate DID in the analysis, we used a previously reported fluctuation-regulated quantum master equation. The existence of the optimum drive amplitude implies that the qubit gate operations would have an optimal clock speed. For efficient implementation of quantum computation, precise knowledge of this clock speed is essential. In the presentation, we would also emphasize on the generic nature of the results achieved for the gate operations on single as well as multiple qubit systems.